The present invention relates to using systems and methods for filtering out coherent noise sources in detection systems. Detection systems can use directivity, frequency diversity, signal integration, and various signal processing techniques to overcome noise sources. Current techniques can to some extent be effective at filtering out random noise sources, but are vulnerable to false alarms caused by coherent noise sources. These vulnerabilities are further increased by an exponential increase in coherent noise sources. For example, collision avoidance systems must perform functions of collision warning, avoidance, and mitigation in a high coherent noise environment. Sources of coherent noise include, but are not limited to aviation radar systems, ship navigation radar systems, cell phones, and other collision avoidance radar systems. In this example, an operator or driver of a vehicle having an antenna or a communication system receiving such additional coherent noise could have the operator's antenna or communication system overwhelmed with interference, e.g., false indications of possible collisions. This undesirable condition could result in control systems malfunction, damage, or injury to the operator or driver. In some embodiments, the term coherent can refer to a comparative attribute of two sets of signals or wave phenomena such as how two sets of signals, one of which is noise, has a similar, identical, or substantially constant difference in attributes such as frequency, phase, or amplitude (e.g., two sets of coherent signals, one of which can be coherent noise, having the same or substantially the same phase or difference in phase) or how the two sets of signals are similar or synchronized in some way.
In an illustrative embodiment, a pulsed electronic signal receives varying phase shifts for each of its pulses prior to transmission. When coherent noise interferes with the transmitted signal, received signal receives a phase shift opposite of that applied prior to transmission such that the electronic signal is restored and the coherent noise becomes non-coherent. In another embodiment, width of each transmitted pulses can be varied prior to transmission, but a constant midpoint-to-midpoint time is maintained. After receiving a signal with coherent noise interference, the midpoints of the pulses are aligned causing the coherent noise to become non-coherent.
Another exemplary embodiment can have different systems, such as described or shown in FIG. 1, which generates phase shift sequences that are applied to outgoing emissions, e.g., radar or otherwise, so that emitters have a different phase shift sequence applied to their outgoing signals.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.